Ink Holdout and Dot Gain When a Stock Changes Grade
Changing stock grades alters micro-porosity and light scattering, shifting ink holdout and dot gain, requiring immediate press curve and ink film adjustments.
Print Contrast
Visual Metric
Quantitative measure of the shadow detail and the ink density of a printed image evaluates the clarity of the reproduction. Calculating print contrast involves comparing the density of a solid ink area to the density of a seventy-five percent halftone tint. This value indicates how well the printing process maintains separation between the dark tones and the solid black or color.
Measurement Technique
A densitometer is used to capture these readings from a standard color bar located on the edge of the sheet. High values suggest that the shadows are open and detailed, while low values indicate that the dots are filling in and losing definition. This metric is sensitive to changes in ink film thickness and press pressure, making it a reliable indicator of optimal ink levels during a production run by providing a clear target for the operator to maintain across different shifts.
Quality Assessment
Optimal results are achieved when the ink density is high enough for impact but not so high that it causes excessive dot gain. Substrates with high ink holdout typically produce better results because the ink remains on the surface. Printers use this data to adjust the ink-water balance or the blanket pressure during a production run.